Initial Bring-Up Test

INTRO

At last, the time has arrived to test your circuit prototype! This phase brings a mix of excitement, anticipation and cautious optimism. But rather than simply throwing the power switch, a more sequencial approach may not only spare you damaged components, but also make easier work of debugging any problems.

A minimum bring-up plan typically includes

• STEP 1:  VISUAL INSPECTION
• STEP 2:  RESISTANCE CHECK
• STEP 3:  POWER-UP
• STEP 4:  INITIAL SOFTWARE RUN
• STEP 5:  DIGITAL I/O CHECK
• STEP 6:  ANALOG INPUT CHECK

For a more complex designs, you can expand the steps above to bring up additional components and characteristics - firmware, power supplies, sensors, actuators, clock edges, noise, etc.

The only Test Equipment you'll need here is a basic inexpensive Multimeter (<$10) you can find in hardware and online stores.

 

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ANALOG + ARDUINO SCHEMATIC

Here's the schematic of our Digital Voltmeter showing the Solderless Breadboard and connections to the Arduino UNO Board.

 

PROTOBOARD + ARDUINO LAYOUT

Check out this suggested physical layout of the voltmeter. However, you can arrange parts and wire the circuit anyway you prefer!

 

STEP 1:  VISUAL INSPECTION

You'd be surprised how many times you'll find components and wires incorrectly installed, reversed or completely missing. Better to discover these mistakes before you apply power and damage components. A few minutes of inspection can prevent needless money spent and time lost waiting for replacement parts!

• Check for components incorrectly inserted, or reversed (SW1,SW2)
• Verify jumpers correctly wired
• Verify Arduino connector pins +5V and GND wired correctly to Breadboard power busses RED and BLK

 

STEP 2:  RESISTANCE TEST

One simple sanity check of correct wiring involves measuring the DC resistance between +5V and GND. Why? A short circuit (low resistance) here may draw dangerous amounts of current causing heat damage to a component or the Arduino's +5V Supply.

• Test with circuit power OFF - no USB connection to the Arduino UNO
• Set Multimeter to DC Resistance - 1k Ohm Range
• Place meter's RED and BLK leads to the +5V and GND on the Arduino or Breadboard.
  • Should be 100s or 1000s of Ohms.
  • <100 ohms could draw too much current.

 

STEP 3:  POWER-UP

One of the scarriest moments in a project happens when you first apply power! Will it do anything? Will it sizzle and smoke? Will it bring the power supply down? This moment is worthy of a cautious approach.

• Momentary Power Test - plug the USB cable IN (2-3 seconds) and OUT of the Arduino.
  • Verify the Arduino LEDs have normal brighness.
  • Dim or dark LEDs indicate some wiring / component issue to resolve
• +5V Supply Test - Set Multimeter to DC Volts. Plug in USB cable into Arduino and measure the voltage between +5V and GND.
  • Verify the supply is +5V +/-0.2V.
  • A low voltage indicates a heavy current draw on the supply. Remove USB cable and check components / wiring.
• Thermal Test - Place your finger on various components (Rs, Cs, ICs).
  • Verify no components are warm or hot to the touch.
  • Warm components indicate unusually high current draw. Remove USB cable and check components / wiring.
  • A Thermal Imager is ideal if budget allows, but fingers serve as handy thermal sensors.

 

STEP 4:  INITIAL SOFTWARE RUN

Plenty of excitement happens around running the software code - the central controlling agent of the digital voltmeter.

The Initial Software Test selects the 4V or 20V Ranges manually by setting the variable Vrange in the code to 0 or 1. (The pushbutton SW3 for range select is tested later in the Basic Voltmeter.)

• For a quick software review, see the Initial Software Test.
• Open the Arduino IDE Software and load the sketch DVM1_initial_test1.ino.
• Click the Upload Button and Serial Monitor Button to observe the printout data.
  • Verify the print statements show running values for Vinput and ADCword every 0.25s.
  • If no output observed, check for proper code file loaded and look for clues in compile / load errors.

 

STEP 5:  DIGITAL I/O CHECK

The Digital hardware plays a huge supporting role by configuring the Analog hardware, especially true here by setting up the voltage divider taps. 

• SWITCH CONTROL TEST - Set the Multimeter to DC Volts and connect the BLK lead to GND. Connect the RED lead to test points listed below.
• Set Vrange = 0 in the setup() code and click the Upload Button.
  • Verify D12 = 0V (SW1 ON) and D13 = +5V (SW2 OFF).
  • If incorrect, check wiring to Switches and code.
• Set Vrange = 1 in the setup() code and click the Upload Button.
  • Verify D12 = +5V (SW1 OFF) and D13 = 0V (SW2 ON).
  • If incorrect, check wiring to Switches and code.

• PUSHBUTTON INPUT TEST.
• Leave SW3 unpressed for an OPEN state.
  • Verify D11 = +5V.
• Push SW3 for a CLOSED state.
  • Verify D11 = 0V.

 

STEP 6:  ANALOG INPUT CHECK

The Analog hardware plays the central role in the actual measurement. However, all three aspects - Software + Digital + Analog - must play well together for the meter's success.

• APPLY VOLTAGE INPUT - Install a wire jumper from the Arduino +3.3V pin to the voltmeter VIN (R1).
• Set Vrange = 0 in the setup() code, click the Upload and Serial Monitor Buttons.
  • Verify Serial Monitor shows Vin = 3.3V approx.
  • If incorrect, check wiring and code.
• Set Vrange = 1 in the setup() code, click the Upload and Serial Monitor Buttons.
  • Verify Serial Monitor shows Vin = 3.3V approx.
  • If incorrect, check wiring and code.

 

HANDS-ON TEST TRACKER

• Record your test results and comments.
• Excel File:  DVM1_Prototype_Test_Tracker.xlsx
  Right Click on the filename, select "Save link as...".
• Use as a template for your own tests.
• Note any unexpected behavior, issues or lessons learned.

NEXT UP

Riding the wave of a successful bring-up, you can move on to fully test the functions in the Basic Voltmeter Test and verify it's Accuracy.

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